Talking to yourself is the preserve of mad men, right? Not according to a new study, which reveals that the seemingly irrational act of chatting to oneself actually improves cognitive function.

The research, carried out by Gary Lupyan and Daniel Swingley, was inspired the pair's experiences of seeing people audibly muttering to themselves when trying to find items on supermarket shelves. To test whether speaking to oneself was actually beneficial, Lupyan and Swingley devised a set of experiments.

In one experiment, volunteers were shown 20 pictures of everyday objects of the same kind and asked to search out a specific one. Initially participants were shown a piece of text telling them which object to find and left to complete the task in silence. Then, in subsequent tests involving different objects, the participants were asked to repeatedly say the name of the object they were searching for. Across the board, the objects were found more quickly when participants were speaking to themselves.

In a second experiment, the volunteers were made to perform a virtual shopping task. Here, they were presented with a wide range of objects typically found in a supermarket, and asked to locate a particular item. Again, they performed this task in silence and whilst talking to themselves. Again, when participants spoke to themselves they found the object more quickly—but only when they were familiar with the name. So, repeating the word "coke" helps you zero-in cola, but muttering "RIM PlayBook" if you've never heard of one—and who has?—won't help you find one any quicker. The results are published in the Quarterly Journal of Experimental Psychology.